Manufacture of organolead compounds



United States Patent MANUFACTURE OF ORGANOLEAD COlVEPOUNDS Sidney M. Blitzer and Tillmon H. Pearson, Baton Rouge, La., assignors to Ethyl Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application March 28, 1955 Serial No. 497,382

Claims. (Cl. 260-437) With the highest yields obtained thereby, only about 22 percent of the lead present in the NaPb alloy is converted to tetraethyllead. Under conditions of best operation of this process, no one heretofore, as far as we are aware, has been able to increase this yield of tetraethyllead by even a few percent, due to the inherent limitation in yield as is apparent from the consideration of the above equation. It should be noted that in this reaction at least 75 percent of the lead originally employed is not alkylated. Thus, in this reaction, large quantities of lead must be recovered and reprocessed to NaPb alloy in order to make it economical. A further disadvantage of such a large quantity of unreacted lead is that valuable reaction space in the reaction vessel is occupied by materials which are essentially inert for the manufacture of tetraethyllead under present conditions and mode of operation.

Other processes for the production of organolead compounds, and in particular tetraethyllead, have been devised to consume the lead produced in the above equation. While such processes are satisfactory from the standpoint of lead consumption, they suffer an additional drawback in common with the present commercial process in that they require organo halide as the ethylating agent. One such process is that described in U. S. Patent 2,535,190 wherein lead as, for example that produced in the commercial process, is treated with metallic magnesium and ethyl chloride in the presence of a catalyst, preferably an alkyl ether. 'Thus, in this process as well as the present commercial process, the tetraethyllead manufacturing operation is restricted by the necessary balance between the metallic sodium required and the organic chlorine in the ethyl chloride. A classical method for the manufacture of tetraethyllead which likewise requires strict balance between metallic sodium and organic halide, and has the additional drawback of requiring highly hazardous ether in the reaction of the so called Grignard reagent, for instance ethyl magnesium chloride with lead chloride.

It is therefore an object of this inventionto provide a process for the manufacture of organolead compounds which overcomes the above objections to the present commercial process and those processes which have been proposed more recently as an improvement thereover.

process for the manufacture In particular, this invention process for the manufacture vpropyl beryllium,

Particularly, it is an object of the invention'to increase the conversion of lead to tetraethyllead above that obtained in present commercial practice without requiring the use of metallic sodium, metallic lead, or alkyl halogen compounds.

These and other objects of this invention are accomplished by reacting a lead halide with a metallo organic compound of the alkaline earth metal series selected from the group consisting of beryllium, magnesium, calcium, strontium, and barium, and wherein said metallo organic compound contains only alkaline earth, carbon, and hydrogen atoms.

In accordance with this invention, it has been discovered that to prdouce organolead compounds it is unnecessary to start with a lead alloy, or in fact to employ metallic lead at a The process of the present invention can best be understood by considering the chemical equation involved. In general, the process proceeds according to the equation where R is an organic atomic weight greater substituted alkyl radicals. In genlower alkyl radicals having up to Among the aromatic radicals the above reaction are included phenyl and hydrocarbon substituted phenyl radicals having up to 10 carbon atoms are satisfactory. Thus, the compounds MR may be considered alkylating or arylating agents with respect to the lead in the inorganic lead compound. 7

Of greatest current importance from a commercial standpoint is the manufacture of tetraethyllead by the process of this invention. This embodiment can be illustrated by reference to the following equation representing the preferred embodiment.

Illustrative of the alkylating or arylating agents which we can employ are dimethyl beryllium, dimethyl magnesium, dimethyl calcium, dimethyl strontium, dimethyl barium, diethyl beryllium, diethyl magnesium, diethyl calcium, diethyl strontium, diethyl barium, di dipropyl magnesium, dipropyl calcium, dipropyl strontium, dipropyl barium, dibutyl beryllium, dibutyl magnesium, dibutyl calcium, dibutyl strontium, dibutyl barium, diamyl beryllium, diamyl magnesium, diamyl calcium, diamyl strontium, diamyl barium, and the like up to about dioctyl beryllium, dioctyl mag nesium, dioctyl calcium, dioctyl strontium, dioctyl barium, diphenyl beryllium, diphenyl magnesium, diphenyl calcium, diphenyl strontium, diphenyl barium, beryllium, dibenzyl magnesium, dibenzyl calcium, dibenzyl strontium, dibenzyl barium, ditolyl beryllium, ditolyl magnesium, ditolyl calcium, ditolyl strontium, ditolyl barium, diphenethyl beryllium, nesium, diphenethyl calcium, diphenethyl strontium, diphenethyl barium, dibutylphenyl beryllium, dibutylphenyl magnesium, dibutylphenyl calcium, dibutylphenyl strontium, dibutylphenyl barium, diethylphenyl beryldiethylphenyl strontium, like. In addition to the normal alkaline earth organo compounds indicated heretofore, the branched chain iso-..

mers can be employed. Likewise, a mixture of two or Patented Nov. 4,195s

preferred embodi- Among the non-aromatic radicals we can employ dibenzyl diphenethyl magmore compounds MR can be employed'along with a redistribution catalyst-to produce organolead compounds containing a multiplicity of hydrocarbon radicals. Thus, by employing a mixture of dimethyl magnesium and diethyl .magneisum and conducting the reaction in the presence of a small quantity of catalyst such as aluminum chloride,'.the' product comprises a mixtureoftetramethy-L lead, .ethyltrimethyllead, .dimethyldiethyllead, methyltriethyllead, and tetraethyllead in an equilibrium :;propor-' tion. Likewise, mixed compounds of the alkaline .eaith series; can-.be employed to .provide mixed organolead compounds. Thus, 'when methyl.,phenyl magnesium is employedin the process of this invention, the principal productis diemthyl diphenyllead. Among the .preferred lead salts,.as shown above, are lead chl ride, lead bromide, lead iodide, lead bromo chloride, lead chloride, and leadbromoiodide'. Other lead halides can likewise be employed with satisfactory results. By theprocess of this invention, as much as.50 percent of the lead in the foregoing lead salts is directly conembodiment, of the lead is in a highly active form as lead metal and is ideally suited for employment in the commercial process employing sodium-lead alloy or in that which proposes the reaction of metallic lead with an alkylating agent'in the presence of magnesium and a catalyst. Conversely, the lead'so produced by this invention can be recycled economically to the present processby conversion to the appropriate lead salt.

Our invention is adaptable to the production methyllead, dimethyldiethyllead, tetraphenyllead, triethylphenyllead and tetrapropyllead. venience in describing our I reference will'be made to tetraethyllead, the most widely known" because of its use as an antiknock agent. Whenever, in the following description, this material is referred to, it is to be understood that other organolead comp unds or mixtures can be'made by our process. Likewise this invention is adaptable to employing broadly the organo alkaline earth fore. However, for convenience, specific reference may be made hereinafter to using diethyl magnesium as this is the preferred embodiment in manufacturing the impor tantantiknock material tetraethyllead.

Generally, the process of this invention is conducted as follows. Into a reaction vessel, preferably a stirred autoclave, is placed the desired quantity of an inert liquid carrier such as, for example, a hydrocarbon of medium boiling range. 'The lead halide in 'finely divided solid form is introduced through a hopper containing a plug cock into the autoclave while agitating to create a suspension thereof in the inert carrier. A suspension of the organo alkaline earth compound in an inert liquid carrier is then fed to the reactor.

reaction temperature, cooling is provided through a jacket in the autoclave. In contrast to other processes'for the manufacture of tetraethyllead, when action-and .prevents the existence of anotherwise hazardousroperation. After completion of therea'ction, the

of organolead compounds generally,'sucl1 as tetraethyllead, tetra-- compounds defined hereto-- This greatly. facilitates control .of: there distillation.

and the organolead by distillation.

The operation described above can be varied and it is not intended that this invention be limited to the specific sequence of addition of the reactants. For example, the suspension of the organo alkaline earth compound can be added to the reactor first and then the finely dividedv lead salt added thereto with agitation. Other modifications will be evident.

While the above operations were discussed in connec-- tion with a batch operation,'they can be successfully adapted to a' continuous process. In addition to applying the .above operation to a continuous process, other modifications of a continuous process can be made, such as first mixing together all the reaction materials and then passing them .continuously through a suitable reaction zone.

It has been indicated that the process of the present invention is conducted in the presence of an ,inert:carrier liquid. Hydrocarbons of appropriate boiling point-with can be chosen so as to provide a-solution:

compose. 1 Other inert carrier liquids are satisfactory and wherettheproduct is a liquid suchas, for example, inthe principalcriterion of choice therefore, of a carrier, isthe. physical characteristic of the organolead compound? produced, and the inertness of the liquid to the organo= Certain of the aforementioned removal facilities. In general, the load on the heat transfer medium is proportional to the concentration orthe reactants and carrier.

luentin the proportion of as much as 1,000 parts per position or undesirable side. reactions.

The alkaline earth well known in the art.

magnesium in the organic diethyl magnesium in dioxane. 'In a more refined-embodiment the dioxane can For convenience in handling,

and. to provide a safe operation, tetra'ethyllead is'first added to the compound removed from the carrier.

to the organolead compound gproducedare satis-:

other means than merely filtration of at completion of the reaction at so as to provide adequate heat organo compounds employedin the process of this Invention can be prepared by methods- For example, diethyl magnesiumbe substantially removed." by

itis preferred to operate in solution prior to the distillation. Thus, a. mixture of diethyl magnesium in tetraethyllead is provided which can be employed particularly for the manufacture of tetraethyllead. For certain of the other alkaline earth metals, the organo derivatives are prepared by the direct reaction of alkaline'earth metal, preferably in the form of'turnings, with an organo mercury compound whereby the desired organo alkaline earth compound is directly prepared in a form suitable for use. It is not. intended, however, that the scope of this invention be limited to any particular method of producing the hydrocarbon cartying reactant.

This invention can be further understood by the following detailed working example of one method of practicing this invention-as directed to the manufacture of tetraethyllead.

Example 1.

To a reactor equipped with internal agitation, external heating means, and a means for cooling was added 87 parts of toluene. Agitation was commenced and 4.17 parts of lead chloride of particle size less than inch were added to the toluene. With continuing agitation, the reactor was flushed with nitrogen and a solution of 1.48 parts of diethyl magnesium in 30 parts of a 50/50 mixture of dioxane and diethyl ether was added to the lead chloride suspension. The reaction proceeded at room temperature while under a nitrogen atmosphere and was continued for a period of 69 hours. At the end of this period a minor proportion of water was added to destroy excess diethyl magnesium. tered to remove solids which are processed for lead value. The filtrate was washed with an equal volume of water. The organic layer was then transferred to a still where, by vacuum distillation, the diethyl ether, dioxane, and toluene were removed from the tetraethyllead. Tetraethyllead was recovered in high yield essentially pure.

In general, the reaction of this process is completed within a relatively short period at elevated temperatures, but a somewhat longer time is required at lower temperatures. In general, a reaction time of between about one-half to twenty hours is employed. In particular, in the manufacture of tetraethyllead with diethyl magnesium and lead chloride, we prefer to employ a reaction time of about ten hours or less.

The pressure employed in the reaction vessel is not critical and is usually the autogenous pressure created by the carrier liquid at the temperature employed. Since organolead compounds are relatively toxic, it is desirable to employ a closed vessel in conducting this reaction which may create an elevated pressure if low boiling carrier liquids are employed.

The temperature required to initiate the self-sustaining reaction of this invention varies with the organolead compound being produced. In general, with the lower alkyl lead compounds such as tetraethyllead, it is preferred to employ temperatures in the range of 25 to 150 C. With aryllead compounds, for example tetraphenyllead, the range of 50 to 150 C.

While it was indicated above that in general a catalyst is not required for the practice of this invention; certain materials do exhibit a catalytic effect upon the reaction and, in many instances, their inclusion in the reaction provides a smoother operation. Typical of such materials are heavy metal iodides as well as iodine itself, organic iodides, certain ketones such as acetone and methyl ethyl ketone, organometallic compounds and ethers and amines as indicated heretofore.

The following detailed examples serve to illustrate additional specific embodiments of the present invention. However, the invention is not intended to be limited thereto.

Example II The reactor comprises an autoclave with internal agitation, external heating means, and a means for cooling.

Attached to the top thereof is provided a hopper for containingsolid reactant having a plug cock by which. the solid reactant is admitted into the autoclave. The autoclave is flushed with dry nitrogen. Then 160 parts of n-hexane are added thereto. Agitation is commenced and 800 parts'of lead chloride of particle size less than is added from .the hopper to the n-hexane. To the suspension thus formed are added under dry' nitrogen a solution of 3 parts of diethyl magnesium in 60 parts of a 50/50 mixture of dioxane and diethyl ether. The autoclave is sealed and the mixture heated to 110 C. Since the reaction is exothermic cooling is applied to maintain the reaction mixture between 110 to 118 C. When the reaction proceeds, alternate heating and cooling is applied as required to maintain this temperature for a total period of 5 hours. At the end of this period, agitation is stopped and the reaction mixture is cooled to-room temperature. The solids are filtered from the reaction mixture, water is added to the filtrate with cooling to destroy excess diethyl magnesium and then the mixture is washed with an equal volume of water. The organic layer is decanted and distilled by vacuum distillation for removal of the hexane, diethyl ether, and dioxane. Tetraethyllead is recovered in high yield.

In place of the hexane ample as an inert carrier employed in the foregoing exliquid, equally good results are obtained when toluene, xylene, triethyl amine, or diphenyl are employed. In addition to the ingredients specified in the foregoing example, thermal stabilizers may be employed, such as for example naphthalene and styrene to permit operation of the reaction at still higher temperatures without concomitant decomposition of the tetraethyllead so produced.

Example Ill When following the procedure of Example II, diethyl beryllium is reacted with lead bromide in essentially stoichiometric amounts in benzene at to C. for

' six hours to produce tetraethyllead in high yield and purity.

When substituting lead iodide in the foregoing example, the reaction proceeds satisfactorily at temperatures in the range of 60 to 100 C. or at the atmospheric reflux temperature of a C to C hydrocarbon petroleum fraction.

Example IV When diphenyl magnesium is reacted with lead chloride according to the procedure of Example II, but at a temperature between 120 and C., tetraphenyllead is obtained in high yield.

Example V Diamyl barium is reacted with lead chloride according to the procedure of Example II. Tetraamyllead is obtained in high yield.

Equally good results are obtained when diamyl strontium is substituted for diamyl barium in the above example.

The following example will demonstrate one embodiment of this invention wherein the organolead compound produced is used as a diluent.

Example VI charged with parts of tetraethyllead in place of the n-hexane. The reaction is then conducted as described.

Tetraethyllead is recovered in high yield.

A particularly advantageous and preferred method of utilizing the process of this invention as specifically. directed to a commercial method of manufacturing tetraethyllead comprises starting with free magnesium and hydriding to produce the corresponding magnesium hydride as the first stage. A-second stage then comprises reacting said hydride with ethylene preferably in the presence of a solvent'suitable as a carrier for the ethyl magnesium, which is thereafter reacted with the lead chloride in accordance withithe foregoing description of the present invention.

We claim: 1. A process for lead compounds which comprises reacting a metallohy 2. The process of claim 1 wherein the alkaline earth series metalis magnesium.

3. The process of claim 1 wherein the reactionis conducted in'theipresence of an inert carrieriliquid at a temperature between about 25 to 150 C. I 4. A process for manufacture of tetraethyllead which comprises reacting diethyl magnesium'iwith lea'd'c'hloa 1 ride. V

5.7 The.process of claim 4 whereinthe reaction conducted in" the presence of an inert carrier liquidand at a temperature between about to C.

References Cited in the file of this patent A V 5 UNITED STATES PATENTS v v 2,786,860 ,Ziegleret a1. Mar. 26, 19,57 3 OTHER REFERENCES Leeper et al.: Chem. Revs. 54, 108 4 

1. A PROCESS FOR THE MANUFACTURE OF HYDROCARBON LEAD COMPOUNDS WHICH COMPRISES REACTING A METALLO HYDROCARBON COMPOUND CONTAINING ONLY THE ELEMENTS CARBON, HYDROGEN, AND AN ALKALINE EARTH SERIES METAL WHEREIN EACH HYDROCARBON RADICAL HAS UP TO ABOUT 10 CARBON ATOMS INCLUSIVE AND IS SELECTED FROM THE GROUP CONSISTING OF ALKYL AND RADICALS WITH A LEAD HALIDE OF A HALOGEN SELECTED FROM THE GROUP CONSISTING OF CHLORINE, BROMINE AND IODINE. 